1. Field of the Invention
This invention relates to a liquid depositing device for automatically depositing a predetermined quantity of sample liquid in a sample container on a chemical assay slide bearing thereon a reagent layer.
1. Description of the Prior Art
Qualitative and/or quantitative determination of a particular chemical component in a liquid sample is widely used in various industrial fields. Especially, in the fields of biochemistry and clinical medicine, quantitative determination of a particular chemical component or particulate substance in body fluids such as blood or urine is extremely important.
Recently, there has been put into practice a dry type chemical assay slide by which a particular chemical component or material component in a liquid sample can be determined by depositing a droplet of the liquid sample on the slide. Japanese patent publication No. 53(1978)-21677, Japanese Unexamined patent publication No. 55(1980)-164356, for example, are referred to. By using such chemical assay slides, liquid samples can be assayed more easily and more quickly in comparison to the conventional wet analyzing process, and accordingly, the chemical assay slide is conveniently used in medical facilities, laboratories and the like where a large number of samples must be assayed.
When a liquid sample is assayed using the chemical assay slide, a measured quantity of the liquid sample is deposited on the slide and the slide is held in an incubator for a predetermined time at a constant temperature to permit reaction to cause coloration, and then light including a wavelength selected previously depending on the components of the liquid sample and the reagents contained in the reagent layers on the slide is projected onto the slide to measure the reflection density thereof.
The quantity of the sample liquid to be deposited on the slide must be measured with a high accuracy since the reflection density differs depending on the quantity of the sample liquid. Accordingly, there have been proposed various instruments such as a pipet for depositing the sample liquid with a high accuracy. For example, there has been known a pipet employing a piston/cylinder mechanism in which sample liquid is sucked into a tip mounted on the front end of the pipet by moving rearward the piston and then discharged from the tip to be deposited on a chemical assay slide by moving forward the piston.
However, such pipets are generally manually operated and are not suitable where a large number of samples must be assayed. Further, such a manually operated pipet is disadvantageous in that the quantity of the sample liquid which can be deposited at one time is fixed and accordingly the pipet must be changed according to the quantity of sample to be deposited. Though some of the known systems can automatically deposit sample liquid, the quantity of the sample liquid to be deposited cannot be freely controlled in any of the known systems.